The Human Genome Project, by potentially elucidating the human genetic material in greater detail, and at a greater level of sophistication, than ever before has concentrated attention on the role of genes in the origin of human traits, including complex behavioral traits. Assertions of the primacy of genes are claims of "genetic reductionism" because the traits in question are, in the final analysis, being "reduced" to genes. The general aim of this project is to analyze the nature of genetic reductionism and to provide a method for adjudicating controversies over claims of the reduction of traits, including complex human mental and behavioral traits, to a genetic basis. In order to achieve this aim, this project will first provide a conceptual analysis of "genetic reductionism." This analysis, which will use standard philosophical strategies of explication, will try to distinguish genetic reductionism from physical reductionism and then place it in the context of philosophical explorations of causation and explanation. It will also try to present the current disputes in the context of traditional "nature- nurture" and "heredity-environment" debates. This analysis will then be used to assess the role played by genetic reductionism in HGP. Next, this project will trace the history of genetic reductionism in twentieth- century biology and, using the analysis that will have been developed, attempt to judge its successes and its failures. The relative success of genetic reductionism in the past will be suggested as a heuristic measure of the probability of its success in HGP. Some suggestions for future re,search strategy will emerge from this historical exploration. Finally, this project will compile lists of exemplary cases where either genetic reductionism has been successful, justifying the identification of a trait as genetic or those where it has failed. These lists, and the accompanying analysis that will have been developed will potentially be useful for the clarification of more controversial and ambiguous cases such as complex human mental and behavioral traits. It is likely, though by no means certain, that many of these complex traits will not be straightforwardly genetic (in the sense that many physical traits are) but also that different complex traits fail to be genetic for different reasons. If such a result is obtained, it will lead to a significant clarification of current disputes about the genetics of alcoholism, mental disease, etc.